This disclosure is directed to a chuck jaw mounting apparatus for use with a rotating machine tool or stationary and more particularly to a set of soft jaws which are anchored in a fixed relationship to radially expanding master chuck jaws.
In machine tools, it is necessary to hold a work piece. The work piece must be positioned concentric about a centerline axis of rotation. The axis of rotation must also be aligned with the dead or live center of the machine tool. This can involve mills and lathes both. In a typical application, a lathe equipped with a headstock includes a rotating spindle which is threaded to a chuck mechanism. The chuck mechanism supports a set of master jaws which expands radially outwardly to grasp the work piece. Speaking very generally, the work piece may include a central opening so that the jaws are expanded on the interior into a gripping position. Generally, the jaws expand radially outwardly until an tight grip is achieved. The grip accomplished in the system enables holding the work piece upon expansion of the jaws.
Because different work pieces require different configuration such as shoulders, different diameters and so forth, many times expendable soft jaws are attached to the master jaws. A setup is required each time the soft jaws are replaced on the master jaws for alignment. Frequently, the soft jaws must be remachined to have precise alignment. One object of this invention is to reduce the alignment error of repetitive setups.
The soft jaws can be blanks i.e., a set of N jaws may be installed where N equals a whole number positive integer. N typically will be 3 and 4 and not more than 6 jaw pieces. If four jaws are used, each will encompass an arc of about 90.degree. minus a small gap for clearance between adjacent jaws. Typically, a set of jaws is assembled for holding a work piece having an internal diameter within the specified range. One range can be 2-4 inches, and a larger version can then accommodate 4-6 inches. Another version which is larger yet and operating in the same fashion can accommodate larger sizes. The blanks are provided so they can be temporarily installed, measured and then cut to a specified or precise diameter. For instance, a set of blanks might normally accommodate a nominal 8 inch work piece. Given a work piece which requires jaws having an original diameter of 8 inches, they can be machined to any diameter which is less than that to accommodate a work piece of 7.000 inches to cite a particular example. Suffice it to say, the individual jaws are machined to provide a locking surface.
A locking surface can typically be part of a cylinder considering all of the jaws together or can be formed with a shoulder. In any case, the exposed soft jaw surface can be machined. It is important that the individual jaws be registered for collective holding of a work piece. The present disclosure sets forth a locking system which secures the individual jaw elements at relative precise locations. It is a location that can be achieved after assembly and disassembly any number of times. On each occasion, the jaws can be removed, perhaps stored for an interval and then repositioned on the chuck so that the jaws are registered. It is somewhat difficult to provide a registration surface for jaws in a circular chuck. One reason for this is that a round surface cooperating with a concentric jaw which is only a segment of a circle can easily elude precise registration. Because of the difficulties that arise from that, it is very difficult to achieve registration when reassembling the jaws. This occurs especially in the case where the jaws are machined so that the gap between the jaws is increased.
The present disclosure sets forth a locking and registration system which is associated with each soft jaw in a multiple jaw arrangement where the number of jaws is given by N. Accordingly, the N jaws are matched with N locking mechanisms in the chuck. The removable and replaceable chuck of the present disclosure thereby enables locking of N jaws in the machine tool. In one aspect of the present disclosure, the N jaws are deployed at equal spacing around the circumference of the chuck assembly. This positions each jaw accommodating a span of 360.degree. divided by N jaws or 90.degree. for a four jaw system. A six jaw system involves 60.degree. spacing to pick another example. In a four jaw system, the present apparatus contemplates positioning of duplicate lock mechanisms at 90.degree. spacing so that the jaws are properly aligned in the chuck assembly.
In one feature of the present disclosure, the several jaws can be assembled in any sequence. Each jaw is positioned on the chuck by placing the jaw on the body of the chuck so that the jaw is anchored without measurement. A lock pin is utilized for alignment purposes and it locks against a tab on the soft jaw. A set screw is used in which a point on the set screws wedges against the jaw jamming it against the lock pin. This assures registration. Registration in three dimensions is normally contemplated so that each detachable soft jaw is wedged against the lock pin, a set screw and a common surface for alignment of all jaws. In other words, there are N lock pins. Moreover, because the locking mechanism is set fixedly when installed by means of a set screw equipped with a pointed tip, wedging action is accomplished which jams the individual lock jaw into a confined location.
Expansion radially outwardly is then utilized in conjunction with the machined jaws so that the outer periphery of the several jaws accomplishes the restraint of the work piece.